Best Practice in Sewage and Effluent Treatment Technologies

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1 Best Practice in Sewage and Effluent Treatment Technologies Contents 1 Wastewater - Introduction Earth s ecological system Water effect on ecology Wastewater generation Wastewater impact and regulations Impact Regulatory environment Planning Planning considerations Financing Summary 9 2 Wastewater Handling System and Quantum Assessment Wastewater system Wastewater system planning Collection systems Wet carriage system Sewer layouts Wastewater transportation and pumping System design wastewater quantity Contribution towards quantity Wastewater generated by population Wastewater generated by industries Addition due to groundwater infiltration Ratio of peak to average flow Estimation of storm water quantity Hydraulic design of sewers Design of wastewater sewers Flow velocity in sewers Velocity in open channel flow Self cleaning velocity in sewer Minimum flow velocity in sewer Maximum flow velocity in sewer Flow in partially filled sewer Construction of sewers Shape of sewers Material of sewer construction 42

2 2.5.3 Cement concrete pipes Asbestos cement pipes Stoneware pipes Cast iron pipes Plastic pipes Sewer operation Manholes and drop manholes Clean outs Street inlets Catch basin Grease/oil trap Flushing tank Ventilators Inverted siphon Ventilation and cleaning of sewers Forced ventilation of sewers Sewer cleaning Precaution during sewer cleaning Summary 56 3 Wastewater Characteristics Wastewater constituents Physical characteristics Color Turbidity Temperature Odor Solid contents Determination of solid contents Chemical characteristics ph value Alkalinity Chlorides Nitrogen Ammonia and ammonium ions Organic or albuminoidal nitrogen Nitrites & nitrates Gases Sulphur Phosphorous Fat, oil and grease Metal and metallic substances Bio-chemical characteristics Dissolved oxygen Chemical oxygen demand (COD) Test for COD Biochemical oxygen demand (BOD) Determination of BOD Factors affecting BOD BOD to COD ratio 78

3 3.4.8 Total organic carbon Relative stability Strength of wastewater Wastewater sampling Summary 81 4 Biological Action in Wastewater Wastewater decomposition Biological decomposition - types Aerobic decomposition Anaerobic decomposition Biological characteristics of wastewater Biological process - terminology Basic microbiology of wastewater treatment Micro organisms Energy/carbon source for micro organisms Important micro organism Bacteria Assessment of bacterial characteristics Detection of bacteria Counting of bacteria Protozoa Characteristics of protozoa Algae Summary Wastewater Disposal Wastewater disposal Disposal on land Process description Land application - types Sewage farming Effluent irrigation Irrigation effluent quality Sewage sickness Disposal by dilution Dilution favourable conditions Standard for disposal by dilution Self purification process of rivers Factors affecting self-purification process Oxygeneration of river water Receiving water effect of discharge Effect of toxic matter Effect of suspended solids Wastewater discharge in lakes Lake system physical and biological Lake productivity and eutrophication Influence of wastewater on eutrophication 129

4 Wastewater discharge in sea Land disposal and dilution methods a comparison Summary Wastewater Treatment Processes Treatment process - selection Classification of treatment processes Preliminary treatment Primary treatment Secondary treatment Tertiary and advanced treatment Wastewater treatment facility - design Design period Preliminary treatment facility individual components Screens Grit chamber Design of grit chamber Construction of grit chamber Mechanical grit tanks Detritus tank Flow equalization system Flow equalization - advantages Flow equalization - disadvantages Equalization system - design Equalization system - construction Oil and grease removal (skimming) Flow measurement system Summary Primary Treatment Sedimentation process Principle of sedimentation Theoretical settling velocity Practical settling velocity Design of sedimentation system Design of continuous flow sedimentation tank Sedimentation tanks construction and operation Dortmund tanks Coagulation assisted sedimentation Common coagulants Advantages of coagulation Disadvantages of coagulation Summary 182

5 8 Secondary Treatment Biological Filtration Introduction Biological digestion Biological treatment process Kinetics of biological process Biological treatment methods Biological treatment by filtration Microbial action Filter media Ventilation Temperature Alkalinity Types of biofilters Contact beds Contact bed construction details Contact bed operation Contact bed performance Intermittent sand filters Intermittent sand filter design Intermittent sand filter construction details Intermittent sand filter operation Trickling filters Trickling filter fundamentals Trickling filter advantages and disadvantages Trickling filter design Trickling filter construction Trickling filter operation Trickling filter types High rate trickling filter Recirculation single and double stage High rate filters - types High rate filters - efficiency Summary Secondary Treatment Activated Sludge Process Introduction Process description Activated sludge process - description Aeration tank Diffused air aeration Mechanical aeration Surface aerator - types Combined aeration Secondary settling tank Sludge handling system Bulking and foaming Rising and denitrification 228

6 9.5 Activated sludge process design parameters Modified activated sludge process Tapered aeration process Step aeration process Contact stabilization process Extended aeration process Modifications in extended aeration process Activated aeration process Complete mix process Nutrients removal Process of denitrification Process of phosphorous removal Activated biofilter Trickling filter activated sludge process Trickling filter activated sludge process design consideration Fixed film activated sludge process Processes with internal suspended packing Processes with internal fixed packing Process control Summary Disposal of sludge Introduction Types of sludge Sludge treatment Sludge thickening Sludge digestion Anaerobic digestion Sludge loading Mixing in a digester Control on ph Temperature - effect Aerobic digestion Digestion tank construction details Design parameters Sludge conditioning Sludge drying Sludge drying beds - features Sludge drying beds - design Sludge disposal techniques Dry sludge - composting Wet sludge Burial Dumping into the sea Incineration Multiple hearth furnace Summary 266

7 11 Miscellaneous Treatment Processes Introduction Rotating biological contactor RBC - process RBC performance Intake works RBC with septic tank RBC design parameters Wetted surface area Effect of staging Nitrification Effect of population and flow variation Effect of temperature Effect of rotating speed Operational considerations Septic tank Septic tank - design Capacity and size Design of inlet and outlet Construction and operation Disposal of septic tank effluent Imhoff tank Imhoff tank construction and operation Stabilization pond Oxidation pond Effluent discharge from stabilization/oxidation pond Aerated lagoon Low cost sanitation techniques Septic tank Pour flush toilets Aqua privy toilets Ventilated improved pit latrine Mini aerobic digestion system Summary Advanced Wastewater Treatment Techniques Introduction Technologies for advanced treatment Suspended solids removal techniques Depth filter principle of operation Depth filtration design and construction Depth filtration - operation Membrane technology Dissolved solid removal techniques Dissolved organic solids Dissolved inorganic solids Reverse osmosis 295

8 Electrodialysis Ultrafiltration Membrane separation cum biological treatment Process Summary Introduction to Tertiary Treatment and Control Systems Introduction Maturation pond Maturation pond - disinfection Effluent polishing Disinfection through chemicals Chlorination Liquid chlorine Chlorine compounds Factors affecting efficiency of chlorination Types of chlorinator Gas chlorinator Control test - introduction Wastewater sample collection Sampling containers Collection procedure Sample size Sampling method Implication of long duration storage Interpretation of test results Summary Industrial Wastewater Oil and Petrochemical Industrial wastewater Industrial wastewater - characteristics Industrial wastewater treatment process components Oil refinery wastewater Refinery - process Refinery wastewater generation Refinery wastewater characteristics Refinery wastewater treatment Petrochemical plant wastewater Petrochemical plant wastewater generation Petrochemical plant wastewater characteristics Petrochemical plant wastewater treatment 328 Appendices 331